Spraying devices of conventional type, for example, injector sprayers or diaphragm metering equipment, meter relatively imprecisely, that is, as the water flow quantity changes, and as the water flow pressure also changes, the percentage admixture of the dosing chemical changes. The equipment also lacks a shut-off in case of a deficiency of chemical or a drop of water pressure.
In the particular case of portable sprayers used for plant protection, that is, for spraying plants with insecticides or the like, a chemical mixture present in a pressure tank is sprayed by air pressure via a hand nozzle. A disadvantage here is that when the chemical is changed, the tank must be thoroughly cleaned with water. Due to the large internal surface of the tanks and the chemicals that adhere thereto, a relatively large quantity of the chemical is removed during cleaning. This means not only a considerable loss of expensive materials but also pollution of the ground water.
In addition, electrical and mechanical metering pumps have been used for quantity-proportional admixing of a concentrate to a stream of water. A disadvantage of these pumps is that the pump elements, such as the piston and membrane, that is, dynamically pressurized parts, come in direct contact with the respective concentrates. Besides, the power consumption of the pumps is very high, especially when the ratio of concentrate to water is high, because the pressure of the concentrate must be increased from atmospheric pressure to the water system pressure for metering.
Thus, there has been a need to develop an apparatus of the above-mentioned kind with which sprays, such as plant protectants or disinfectants, can be quantity-proportionally metered and sprayed in a manner independent of pressure and rate of flow. In particular, the following requirements should be fulfilled:
1. A given concentration must remain constant during water pressure fluctuations and water flow fluctuations. Also, the concentrate/water mixture must be constant at all times without dosage divergence; PA1 2. It must be possible to operate the device only at a water pressure at which a satisfactory spray pattern can be produced with the nozzle spray head; PA1 3. Upon a deficiency or depletion of chemical, the device must shut off automatically; PA1 4. It must be possible to recover unconsumed concentrate; PA1 5. The force required for metering must be held to a minimum to improve the total pressure loss of the device, and it must be possible to draw the metering energy from the existing water pressure; PA1 6. When chemicals are changed, it must be possible to clean the device easily, in particular, to rinse it with water; PA1 7. It must be possible to make the device portable or stationary; PA1 8. It must be possible to empty the concentrate container completely during operation of the device; PA1 9. The metering pump elements should not come into contact with the concentrate; and PA1 10. It must not be possible to operate the metering deice without the attachment of the vessel intended to receive concentrate. PA1 (a) a pressurized water feed, having a minimum pressure value unit and leading to the mixing chamber of the nozzle spray head, is fed first to a water motor provided with a drive piston driven by the pressure of the inflowing water and then to a double-action metering pump having a metering piston coupled with said drive piston of the water motor, the cross-sectional area of the metering piston and the cross-sectional area of the drive piston being in a predetermined ratio; PA1 (b) a flexible container for chemicals residing in a detachable rigid vessel connected to a metering outlet line of the metering pump, said flexible container being emptied via a container outlet valve and a container line into the mixing chamber of the nozzle spray head by displacement by means of water metered through the metering outline line; and PA1 (c) a feedback line leading from the metering pump cylinder to a pressure water connection valve that closes in case of overpressure in the metering pump to shut off inflowing water.